diff --git a/src/ca65/expr.c b/src/ca65/expr.c
index 812b6e90c..5dcf5ca71 100644
--- a/src/ca65/expr.c
+++ b/src/ca65/expr.c
@@ -496,7 +496,7 @@ static ExprNode* FuncIsMnemonic (void)
     /* Skip the name */
     NextTok ();
 
-    return GenLiteralExpr (Instr > 0);
+    return GenLiteralExpr (Instr >= 0);
 }